Microbial-induced Cations Exchange for Sustainable Reclamation of Saline Soils

Abstract

A laboratory incubation study was carried out at TNAU, Coimbatore (2021–2022), to assess the impact of two salt-tolerant microbial inoculants CSR-GROW-SURE (containing Lysinibacillus fusiformis (CSR-A-11), Lysinibacillus sphaericus (CSR-A-16), and Bacillus licheniformis (CSR-M-16) and TNAU culture (consisting Bacillus subtilis) applied at 1, 2, and 3 L ha⁻¹ on saline soils with EC levels of 4.03, 5.01, and 6.02 dS m-1.The study evaluated changes in exchangeable cations such as calcium (Ca2+), magnesium (Mg2+), sodium (Na+), and exchangeable potassium (K+) at 30, 60, and 90 days after incubation (DAI) under 100 % field capacity (FC). At 90 days after incubation (DAI), the application of CSR-GROW-SURE at 3 L ha-1 resulted in reduction of exchangeable cations, with Ca2+ decreasing by (8.30, 4.50 and 5.76 %), Mg2+ (8.20, 4.57 and 5.71 %) and Na+ (27.36, 26.56 and 26.27 %) at salinity levels of 4.03, 5.01, and 6.02 dS m-1 respectively, compared to the control. In contrast, there was a significant increase in exchangeable K+, with improvements of (15.89, 17.31, and 15.02 %) at the same salinity levels, representing enhanced soil nutrient balance. A comparable trend was observed with the TNAU culture at 3 L ha-1, where reductions in Ca2+ (8.11, 4.27 and 5.69 %), Mg2+ (8.01, 4.29 and 5.59 %), and Na+ (26.45, 26.04 and 25.64 %) were recorded, along with increases in K+ (15.44, 17.03, and 14.72 %) across the corresponding salinity levels. These trends suggest that microbial inoculation modifies ionic dynamics by decreasing exchangeable sodicity and enhancing potassium availability under saline stress. These results confirm that both microbial inoculants at higher application rates were effective in improving the chemical properties of saline soil by reducing exchangeable cations (Ca2+, Mg2+ and Na+) and increasing exchangeable K+, with the most significant changes observed at 90 DAI.